Air flotation (AF) systems such as Dissolved Air flotation (DAF) and Cavitation Air flotation (CAF) have been used in food processing plants and waste water treatment plants for many years. The purpose of AF systems is to reduce BOD (biological oxygen demand), COD (chemical oxygen demand), FOG (fats, oils and grease), SS (suspended solids), and TKN (total Kjeldahl nitrogen) in the waste water passing to sewage treatment or to discharge. Most food processing plants use large volume water to wash food products and produce waste water with high BOD, COD, FOG, SS, and TKN. Waste water is a major issue in food industry, which effects environment. The oily AF sludge (it is also often called AF skimming) from an air flotation system has large volume such as about 15,000 tons (or 30,000,000 pounds) per year from an average animal processing plant. The sludge is often processed into hot liquid oil by heat, vacuum, and centrifuge processes. The hot liquid oil becomes viscous fat after cooling down at room temperature. It is needed to be heated again to become a liquid oil form before applications. Customers need to spend more energy cost for the heat and stirring equipment for the agitation. Some farms have no the capacity to heat and to agitate AF sludge fat product. AF sludge fat has low value compared with normal fat ingredients. The sale price is only about ⅕ to ⅓ of normal fat or oil ingredients.
Vegetable soap stock such as soy, corn or canola oil soap stock is a major byproduct produced during vegetable oil process. The byproduct is an oily sludge, which normally has about 45% fat and 50% moisture. The oily sludge is not possible to be processed into a dry and non-oily product by a normal dry process. The sludge is often to be adjusted to low pH for low viscosity, heated and vacuumed into hot liquid oil after removing the moisture. It often becomes viscous after cooling down for a period of time and needs to be heated again into a liquid oil form before applications.
Over the years, various attempts have been made to convert and to improve oil ingredients into non-oily solid products. Some new processing methods to convert oily ingredients into non-oily products with some protein ingredients have been invented by author. It is necessary to process the oily ingredients into non-oily products without the protein ingredients to meet practical situations. A number of patents have been issued for these attempts. U.S. Pat. No. 6,576,667 discloses a method for manufacturing fatty acid salts from high glyceride content oils with eicosapentaenoic acid and docosaheaenoic acid into a calcium salt product by adding 2 to 3 equivalents of calcium oxide relative to the oils and 2 to 5 equivalents of water relative to the calcium oxide so that the calcium oxide hydrates and neutralizes the fatty acids to form calcium salts. The reaction is completed at 210-240 degree F. U.S. Pat. No. 6,368,657 discloses a method for converting oily DAF sludge into a non-oily solid fat-protein product with the protein precipitation process to binding the fat under the heat treatment by the author. The product has the bypass protein (95%) and bypass fat (85%) for ruminant animals. U.S. Pat. No. 6,229,031 discloses a method for preparing fatty acid glycerides into a calcium salt product by adding calcium oxide and water and then heating to a high temperature such as 150 degree C. at which the fatty acid glycerides saponify to form fatty calcium salts. The calcium soap salt product has the bypass function for ruminant animals. U.S. Pat. No. 5,514,388 discloses a process to treat protein with a base to increase the pH to such as 11 at first. Then a fat is added into the alkali protein. The protein firm gel is formed when the pH is lowed to 3 to 5. U.S. Pat. No. 5,496,572 discloses a process to form a ruminant feed stuff by a homogeneous mixture of animal or vegetable protein material, one or more fatty acids, and a calcium or magnesium compound by an extrusion process. U.S. Pat. No. 4,427,572 discloses a process to prepare a calcium soap product by saponifying an organic carboxylic acid with calcium hydroxide in a dipolar aprotic solvent such as acetone. Then the calcium soap product are separated from the reaction mixture and excess acetone is removed from the calcium soap product. U.S. Pat. No. 4,217,370 discloses a process to treat protein with a base to increase the pH to such as 11. Then a fat is added into the alkali protein. The protein and fat are mixed together before any pH change. The protein gel is formed when the pH is lowed to the isoelectric point. U.S. Pat. No. 4,216,234 discloses a process to render albumin medium with strongly alkaline such as 11.5 prior to the formation of a fat dispersion or emulsion, and thereafter the dispersion or emulsion is heated to form a gel product. U.S. Pat. No. 4,138,505 discloses a process to heat animal blood to a temperature in the range of from about 20 degree C. to 60 degree C., to adjust the pH to a level ranging from 9 to about 13 to form a blood solid gel, and thereafter recovering the fat-protein gel.
AF sludge fat and vegetable soap stock are low-value liquid fat or oil products. They also are not easy to be handled, delivered and applied to feed applications. They need to be reheated in most applications. It needs to develop some practical and economical methods to process AF sludge fat and vegetable soap stock into non-oily solid products without combining with a protein ingredient.